It is common practice to drive a wheel with traction means such as a combustion engine, a (jet) turbine or for example an electric motor. The drive is connected to the wheel by means of a reduction gear, usually a gearbox having an acceleration, or a V-belt or the like.
In the parent application to the present case (U.S. Ser. No. 10/205,405), an electric motor is mounted into a wheel.
It is an object of the invention to realise a traction system having an improved efficiency and more versatile application possibilities.
To that end the invention provides a traction assembly comprising a wheel comprising a wheel rotational axis and a traction means comprising an electric motor which, when in operation, exerts a torque on the wheel, wherein the traction ratio, being the arm of the torque divided by the radius of the diameter of the wheel, is larger than 0.57.
By choosing such a ratio of the arm relative to the diameter of the wheel it is possible, on the one hand to create a workable situation in which way a practical vehicle can be made, and on the other side to achieve optimum efficiency.
Tests and research with regard to the electric motor within the wheel as described in the aforementioned parent application, led to the discovery and the insight that the efficiency with respect to the embodiment described in the parent application could still be further improved when the arm of the torque is as close as possible to the diameter of the wheel.
Furthermore, side effects appeared to occur, which drastically reduced the net losses of other energy-using components. Due to the efficiency improvement an engine with smaller a capacity than expected could be deployed for traction. As a result the required battery capacity could also be reduced. In addition, several components, such as the battery charger and the other electronics, could be reduced in size and/or weight. As a result the required engine capacity could yet again be further reduced. Finally a considerably more efficient traction than could theoretically be calculated, appeared possible.
As a result energy efficiency improvements could be realised that went well beyond what until then had been calculated and known.
The arm has been determined here by the distance between the centre of the drive shaft or rotor and the line of action of the force exerted by the traction means on the drive shaft or rotor to rotate the drive shaft or rotor.
A traction device according to the invention as to structure can very well be realised when using an electric motor.
When applying for example an electric motor provided with a stator having windings and a rotor mounted around it having permanent magnets (a so-called: “buitenloper”), wherein the stator is stationary and connected to a vehicle and the rotor having the permanent magnets revolves around the stator and is connected to the wheel shaft and the wheel, the arm will be half the inner diameter of the rotor, i.e. the inner radius of the rotor. Such a configuration makes it possible to realise a traction device according to the invention, with a surprisingly high efficiency.
The electric motor may also comprise windings that are mounted on a drive shaft like a rotor and the permanent magnets may be statically mounted outside the stator. In this case, the arm is half the diameter of the rotor. Variations on these concepts are possible.
In one embodiment in which the traction means comprise an electric motor, the stator will include the windings and the rotor will include the permanent magnets. This eliminates the need for complex supply of electric power, and the construction of the electric motor can be simple. Furthermore, the connection to or inclusion in a vehicle can be simple. Once again a “binnenloper”, where the rotor revolves within the windings, as well as a “buitenloper”, where the rotor revolves around the windings, could be chosen. The “buitenloper” is preferred to be able to realise the largest possible traction ratio.
In an embodiment the wheel is provided with a tyre, preferably a pneumatic tyre. In that case, the radius of the wheel also includes the thickness of the tyre. For a vehicle provided with a tyre, the choice for a traction assembly according to the invention is even less obvious.
In a further embodiment, for the sake of a simple assembly, the traction means have been mounted by means of connection means, which permit an angle between the wheel shaft and the drive shaft of the traction means. Examples of such connection means are a cardan transmission and a so-called “homokineet”, a type of axis provided with a joint, or similar means.
In an embodiment the windings have been statically connected to the vehicle, and permanent magnets have been arranged around the windings and connected to the drive shaft. This makes a simple construction possible, because the supply of electric power is simple. In addition the rotor on which the magnets are mounted can be designed using lightweight materials.
In an embodiment of the traction assembly, according to the invention, the traction ratio is larger than 0.65. With a proper choice of the traction means this ratio appeared feasible. In a further embodiment the traction ratio is larger than 0.7. In this case, high demands will be placed on the design of the traction means.
In an embodiment the traction ratio is smaller than 1.0, preferably smaller than 0.95. In this case, a good selection needs to be made of the material and type of wheels. Applying pneumatic tyres for instance will necessitate extraordinary types and models of pneumatic tyres.
In an embodiment of the traction assembly according to the invention, the traction means comprise an electric motor. Experience has shown that an electric motor is particularly suited for use in a traction assembly according to the invention. For instance an electric motor has high torque at low revolutions. Furthermore, because of a careful design it will be possible to realise a traction complying with the demands made by the invention on the traction ratio.
In a further embodiment the electric motor is a synchronous motor provided with permanent magnets. This simplifies the design of the motor. Moreover, using permanent magnets further allows a sufficiently compact construction of the motor.
In an embodiment of the traction assembly, according to the invention, in which the traction means are an electric motor, said electric motor comprises a stator provided with windings, which with respect to a vehicle are statically arranged in the vehicle, and a rotor provided with permanent magnets. The electric motor can thus be built sufficiently compact to be used in the invention.
In an embodiment the traction means comprise operating and control means for the operation of the electric motor within the stator and preferably against the stator.
In a further embodiment the rotor is arranged coaxially around the stator and connected to a drive shaft of the electric motor (“buitenloper”).
In an embodiment the traction means are mounted adjacent to the wheel.
In an embodiment the traction means comprise a drive shaft, and the drive shaft and the wheel shaft are situated in line and in each other's extension.
In an embodiment the drive shaft and the wheel shaft are connected for direct traction.
In an embodiment in which the traction means comprise a drive shaft, the drive shaft directly drives the wheel shaft. In a particular embodiment of this, the drive shaft is the wheel shaft.
In an embodiment of the traction assembly, in which the traction means are an electric motor provided with permanent magnets, the permanent magnets are connected to the wheel shaft.
The wheel shaft and the drive shaft may possibly be connected by means of a connection that permits the longitudinal axis of the wheel shaft and the longitudinal axis of the drive shaft to be at an angle that does not equal 180°. A cardan transmission and use of a so-called “homokineet”, a type of axis which is provided with a joint, are examples of such a connection.
In an embodiment the efficiency, and in particular the energy consumption, of a vehicle comprising such a traction assembly according to the invention or described above can be improved even further, when the traction means or driving means comprise an electric motor which is adapted to provide a maximum nominal or rated torque of at least 0.3 Nm/kg of vehicle mass. Even better efficiency is possible if the maximum nominal or rated torque is at least 0.4 Nm/kg of vehicle mass. This torque is the maximum rated torque. An electric motor can provide, during a short period of time, usually not more than several minutes, up to twice this maximum rated torque. It was discovered that this seemingly large over dimensioning provides a large efficiency advantage, especially in combination with the traction ratio.
Another aspect of the invention regards a traction assembly for a vehicle, comprising a wheel provided with a wheel shaft, and an electric motor comprising a drive shaft, a rotor and a stator, in which the drive shaft is connected to the wheel shaft for direct traction and the electric motor is arranged adjacent to the wheel.
Surprisingly energy efficient traction is thus made possible.
In an embodiment the wheel shaft and the drive shaft are arranged in line. In addition other embodiments as mentioned above are possible.
The invention further relates to a wheel provided with electric driving means in the wheel as well as a method for coordinating the number of revolutions of at least two of such wheels attached to one vehicle.
From the literature wheels provided with electric driving means in the wheel are known. In particular wheels are known that are provided with electro motors in the wheel. Examples of such wheels can for instance be found in DE-A-2719736, DE-A-4404889, FR-A-2561593, U.S. Pat. No. 4,585,085 and WO-A-95/16300.
One of the problems occurring in the known wheels is the coordination between wheels when more than one driven wheel is used in one vehicle.
Another problem occurring in the known wheels provided with driving means is that control means are necessary. Such control means are arranged outside the wheel in a vehicle. This renders the building of an electronically driven vehicle a complex megatronic venture. WO-A-95/16300 tries to solve this by arranging a part of the control electronics within the wheel. Using several such driven wheels in one vehicle is not possible however.
It is an object of the invention to provide an electrically driven wheel of high efficiency.
An additional object of the invention is to provide a wheel that is easy to mount.
Additionally it is an object to develop a wheel that offers freedom of design of a vehicle.
Another object is a wheel that is simple to replace and demount.
Another object is offering a wheel provided with driving means which in cooperation with other similar wheels can be deployed in one vehicle.
Said problems are at least partially solved and at least a part of the advantages achieved by means of the wheel according to the invention.
To that end the invention relates to a wheel provided with electric driving means in the wheel, control, measuring and operating means in the wheel for operating the electric driving means and data communication means in the wheel.
The current invention can use the motor and all of its components inside the motor described in this description also as a motor which is located outside the wheel, but directly driving an axis of a wheel.
Additionally the invention relates to a method for coordinating the number of revolutions of at least two wheels provided with electro motors in the wheels and further provided with control, measuring and operating means in the wheels for operating the electric driving means and with data communication means in the wheels, in which physically separated control systems control the amperage in each winding of the electro motors, the control systems in one wheel are operated by an operating system, a measuring system supplies information regarding the magnetic field strength to the control system and supplies the mutual position of the rotor and stator to the operating system, and the operating systems of the several wheels communicate with each other by means of data communication means via a central processing unit.
In an embodiment, the communication means comprises means for establishing and maintaining a computer network. This computer network may comprise two or more wheels according to the present invention, but also one or more computers outside the wheels. Such a computer network may comprise a LAN, WAN, of even the internet. The connection can be made via copper, glassfiber, wireless (i.e., IR, optically, bluetooth, or any other means).
Because of the wheel according to the invention a driving concept has been realised that is efficient, simple to mount and can be integrated in a vehicle.
Because of the method according to the invention it is possible to use several wheels provided with electric drive in one vehicle.
Preferably the wheel comprises a rim which coaxially at the inner side is provided with a rotor with permanent magnets. The rotor and rim are connected to a central shaft, and a coaxial stator is provided with windings. The stator is situated between the central shaft and the rotor and being connectable to a vehicle. In that way the wheel is provided with an electro motor. As a result a simple drive of the wheel is possible. Moreover no transmission is needed, particularly no reducing transmission, in which great power losses have appeared to occur.
More specifically the stator is divided into at least two groups of electrically and physically separated windings and each group comprises at least two windings each having its own control and measuring system, which control and measuring systems are situated in the wheel and the control and measuring systems are operated by an operating system which is also situated in the wheel. As a result a driving system is created that is integrated in a wheel, in which the driving system is very robust and not very sensitive to malfunctioning.
The wheel according to the invention more preferably comprises means for exchanging data with the control, measuring and operating system of other, similar wheels. As a result it is possible to couple several wheels according to the invention to one vehicle, because of which a powerful propulsion of the vehicle can be realised. In order to make the data communication less sensitive to malfunctioning, the means for exchanging data to the outside preferably are optical communication means.
In order to let either several wheels or one wheel according to the invention communicate with other equipment outside of the wheel, the measuring, control and operating systems of a wheel communicate via a central processing unit outside the wheel. In this way for instance several wheels of one vehicle are able to communicate with each other.
In order to further reduce the sensitivity to malfunctioning of a wheel even more, the control system comprises means for controlling the strength of electric current through each winding separately. In this case a winding also means a coil. When a current runs through the coil or winding this results in a magnetic field.
The control systems of the windings are connected to the operating system. Said operating system is hierarchically above the control systems and orders each control system to set and maintain a certain strength of electric current.
The wheel according to the invention is also provided with measuring systems, in which the measuring systems comprise an encoder for measuring the number of revolutions and the angular position of the rotor with respect to the stator, and a current measuring device for measuring the current through each of the windings. As a result the current through each winding can be accurately set and calibrated. Additionally the operating system is able to operate the winding well, and set the phase on each winding for an optimal working of the electric drive. Additionally the measuring system is provided with means for measuring the mechanical torque, preferably by means of strain gauges that are able to measure the strain in material accurate to the nanometer. Such means for measuring strain or torsion, deformation in metal in general, as such are known. A comparison of mechanical resulting torque and accommodated motor power provides an idea of the condition of the wheel.
The encoder preferably is connected to the operating system and the control systems are connected to the current measuring devices. As a result a modular system is created that is not very prone to malfunctioning.
The operating system is connected to a central processing unit outside the wheel by means of the data communication means. As a result the coordination with other systems in a vehicle is possible.
In order to cool the driving means in case of an all to great development of heat, the wheel is provided with cooling means, and if so desired also with active cooling means, such as fans 616. Additionally the wheel may be provided with means for water cooling.
In order to render cooperation of several wheels according to the invention in one vehicle possible, the operating systems in the wheel preferably are provided with a “master” setting and a “slave” setting, in which by means of the communication means the central processing unit is able to have the operating system switch from the “master” setting to the “slave” setting and vice versa. For instance when taking bends either the power demand or the speed of several wheels will vary. In order to make coordination of one with the other possible, the switch from the “master” setting to the “slave” setting and vice versa is influenced by either the power demand or the speed of the wheel. It is preferred here that the wheel demanding the lowest power, i.e. the wheel having the highest speed of revolution, has been set as “master”.
In the method according to the invention it is preferred that the central processing unit has the operating system of the wheel demanding the lowest power function as “master”, and has the operating systems of the other wheel or other wheels, respectively, operate as so-called “slave”. In one embodiment, the master-slave settings may change dynamically during operation of the vehicle, i.e., each time the wheel demanding the lowest power becomes the master, the other wheel(s) will become the slave unit(s). Thus, the master and slave settings can change from wheel to wheel during operation of the vehicle. As a result the driving system is easy to implement and control.
In order to anticipate future situations during driving well, it is preferred that the central processing unit includes data of the wheel struts regarding the angular position when managing the operating systems of the wheels.
The invention further relates to an assembly of at least two wheels according to the invention that are connected to a common central data processing unit by means of data communication means.
The invention further relates to a vehicle wheel having an electro motor in it, in which the electro motor is a more than 8 pole, 3 or more phased, DC synchronous motor.
Additionally the invention relates to a wheel provided with a housing mounted at a rotatable shaft, at the outside provided with a rim with tyre and at the inside provided with permanent magnets, and a housing mountable at a vehicle, rotatably connected to the shaft, provided with control, measuring and operating means and electric means for generating a magnetic field. Because of such a structure the wheel is simple to replace and can be mounted in a modular manner. Additionally a mechanical brake system is easy to mount on the shaft as an extra safety provision.
Additionally the invention relates to a wheel provided with electric driving means in the wheel, means for measuring the mechanically delivered torque, means for measuring the torque by measuring the electrically accommodated power and means for comparing the mechanically delivered torque and the measured electric power. As a result it has appeared possible to detect premature wear and malfunctions in the wheel, even before an actual defect occurs. By means of the communication means a (future) defect can be established even at a distance and possibly be remedied.
Additionally the invention relates to a wheel provided with electric driving means in the wheel, provided with at least two galvanically separated motor windings, at least two galvanically separated power modules and at least two galvanically separated operating units for the power modules.
The invention moreover relates to a wheel strut provided with vehicle attachment means for attaching the wheel strut to a vehicle, and wheel attachment means for attaching a wheel to the wheel strut, in which the wheel attachment means are rotatable about the longitudinal axis with respect to the vehicle attachment means and in which the wheel strut is provided with driving means for rotating the wheel attachment means with respect to the vehicle attachment means.
As a result such a wheel strut is easy to mount on a vehicle, and other means such as a steering means for the vehicle and drive for wheels can easily be coupled.
Preferably the vehicle attachment means and the wheel attachment means are spring-mounted to each other along the longitudinal axis by means of connection means.
Preferably the connection means comprise a splined shaft which at one side is provided with a spline and on the other side is provided with driving means for rotating the splined shaft, and with a spline housing in which the splined shaft is situated and which spline housing at the bottom side is provided with accommodation means for a wheel shaft and attachment means for a wheel, and in which the vehicle attachment means are formed by a sleeve provided with means to connect the sleeve to a vehicle, in which the spline housing with splined shaft is at least partially accommodated in the sleeve, in which the spline housing and the sleeve are spring-mounted to each other by means of spring means, and the driving means are connected to the sleeve.
The structure that can be realised in this way is simple, robust, and can be integrated well in and with existing vehicles and production methods.
In order to attach a wheel the spline housing is provided with a receiving sleeve for a shaft which is positioned substantially perpendicular to the spline housing. As a result it is possible to attach a wheel stably and securely.
Additionally the wheel strut comprises spring means for buffing the vertical movement of the wheel attachment means with respect to the vehicle attachment means.
Preferably the wheel strut is provided with means for communicating with the driving means.
Preferably the wheel strut is provided with means for communication with the operating means of a wheel according to the above-mentioned first aspect of the invention. Preferably the driving means of the wheel strut communicate with the operating means of a wheel according to the invention by means of the central processing unit.
Said aspects of the invention can, if so desired, be combined. For instance a vehicle can be equipped with 2 or 4 wheel struts according to one aspect of the invention, and 4 or more wheels according to the invention. It is also possible for instance that a fork-lift truck is equipped with only one or two wheels according to the invention, but also with two wheel struts according to the invention.
As a result of a high degree of automation the wheel strut and the wheel according to the invention are particularly suitable for use in fully automatically guided vehicles. Operation can also take place by means of a joystick and so-called drive-by-wire, in which the signals of for instance a joystick or steering wheel are converted into (electric or optic) steering signals.
The invention furthermore relates to a particular electromotor, and a vehicle which is driven in a particular way using an electromotor.
In practice electromotors are known in various embodiments. A problem with the known electromotors is that the quantity of torque provided often is difficult to set. In addition the operation of several electromotors often is difficult to adapt to each other. Moreover it is hard to adapt the provided torque of an electromotor to the desired application and to dimension the electromotor such that is can be used for various applications.
It is an object of the invention to at least partially overcome the said drawbacks.
It is a further object of the invention to provide an electromotor that is universally applicable and easy to scale up and deploy, for instance in a vehicle.
It is a further object of the invention to provide an improved vehicle having an advantageous fuel consumption.
To that end the invention provides an electromotor comprising a housing provided with:                a stator connected to the housing and comprising at least two groups of physically separated windings;        a rotor, coaxially and rotatably mounted within the stator and comprising permanent magnets;        control means for controlling the electric current in the windings;        measuring means for measuring the current and the phase thereof through the windings and the angular position of the rotor with respect to the stator;        operating means connected to the control means and the measuring means for operating the electromotor, and        data communication means, connected to the operating means, for communicating data to outside the housing.        
The invention further relates to a vehicle provided with a wheel having a wheel shaft having an axis of rotation and a electromotor provided with a rotor having an electromotor axis of rotation, wherein the electromotor is placed in the vehicle with its axis of rotation mounted above the axis of rotation of the wheel.
By opting for an electromotor according to the invention an electromotor is obtained having an adjustable torque. Moreover it is possible to connect several motors to each other. To that end among others the housing is provided with attachment means.
The placing of the motor in the vehicle makes it possible to make a vehicle having an advantageous ratio between the diameter of the air slit (i.e., the space between the magnet and the windings) and the diameter of the wheel. As a result an energy-efficient vehicle can be developed. Especially in combination with the motor according to the first aspect of the invention, a vehicle having advantageous properties can be developed.
In an embodiment of the electromotor according to this aspect of the invention, the measuring means comprise at least two means for measuring a magnetic field, arranged between two permanent magnets.
In another further embodiment, both ends of the rotor comprise attachment means for a driving shaft.
In a further embodiment one of the attachment means comprises a bush in which a shaft end can be operationally connected to the rotor.
In another or further embodiment, the operating means have a so-called master and slave setting, wherein the operating means can be converted from a so-called master into slave setting, and vice versa, influenced by either the demand for power, the speed of rotation of the rotor or via the data communication means.
In an embodiment, the other attachment end is provided with a homokinete.
In an embodiment, at least two electromotors according this aspect of the invention are assembled together, wherein one electromotor is set as so-called master and the other one or ones as so-called slave, and wherein the data communication means are connected one to the other or others to each exchange data with each other.
In an embodiment of the vehicle, the electromotor axis of rotation is substantially parallel to the axis of rotation of the wheel.
In another embodiment of the vehicle, the rotor is connected to the wheel shaft by means of one or more homokinetes.
The invention additionally relates to a computer provided with software for the operation of one or several wheels as described, and/or for the operation of the wheel strut. Additionally the invention relates to a data carrier provided with such software.